In image sensing devices such as digital cameras, close studies have been conducted on practical application of a shape memory alloy actuator (i.e., a shape memory alloy driver) that moves a lens by use of a shape memory alloy. The shape memory alloy contracts by being applied with a voltage or current and heated. In addition, the shape memory alloy expands by dissipating heat. Thus, by connecting a movable portion such as a lens unit to one end of the shape memory alloy to apply a voltage or current and controlling the amount of current passing, it is possible to perform focusing etc.
The displacement of the shape memory alloy with respect to a driving current varies with the environment temperature. For example, in a case where the environment temperature is extremely low, a driving current larger than normal is needed in order to overheat the shape memory alloy. Accordingly, even if the target displacement is the same, the driving current of the actuator needs to be varied in accordance with the environment temperature.
In relation to the above inconvenience, Patent Document 1 discloses a control device of a unit injector that permits variable control of the amount of fuel injection by use of a shape memory alloy. The control device detects the temperature of the shape memory alloy by use of a temperature sensor or the resistance value of the shape memory alloy. Then, the control device varies the energization amount and the energization time of the shape memory alloy in accordance with the detected temperature to thereby control the amount of fuel injection. As described above, by detecting the state of an object to be controlled and controlling (i.e., performing servo control) such that the object is in a target state, the energization amount etc. (hereinafter referred to as the “drive control value”) is controlled such that it varies in accordance with variation in environment temperature, even if the environment temperature varies.    Patent Document 1: JP-A-2006-189045